Defrosting system and apparatus



1960 E. J. VON ARB ET AL 2,962,870

DEFROSTING SYSTEM AND APPARATUS Filed Jan. 20, 1958 2 Sheets-Sheet 1 x I I7 L /26 I8 25 I5 20 IR 39 A p N 38 E I INVENTORS HOWARD. J. TENNISWOOD EDWQQD. J. VON ARB AT TOR EY S 1960 E. J. VON ARB ETAL 2,962,870

DEFROSTING SYSTEM AND APPARATUS Filed Jan. 20, 1958 2 Sheets-Sheet 2 EXC HANGER T INVENTORS HOWAR D .J. TENNISWOOD EDW$$D .J. VON ARB ATTOR NE S United States Patent DEFROSTING SYSTEM AND APPARATUS Edward J. Von Arb and Howard J. Tenniswood, Adrian, Mich, assignors to Revco, Inc., Deerfield, Mich., a cor poration of Michigan Filed Jan. 20, 1958, Ser. No. 709,999

9 Claims. (Cl. 62-140) This invention relates to refrigerators of the type in which a fiuid refrigerant having a low boiling point is compressed while in the gaseous phase and forced into a condenser where it cools under pressure and thus is transformed into the liquid phase, the refrigerant then being reevaporated and absorbing heat as it returns to the gaseous phase, in which it is again compressed.

' A refrigerator of the type to which this invention relates has a pump, commonly called a compressor, for compressing the refrigerant, a motor for operating the compressor, a heat radiating coil, commonly called a condenser, into which the refrigerant is. compressed by the pump, a restricted passage through which the condensed refrigerant escapes from the condenser into a heat absorbing coil, commonly. called an evaporator, where the refrigerant reverts to the gaseous phase, anda return conduit through which the refrigerant is evacuated by the pump, being recompressed, recondensed, and reevaporated through repeated cycles.

The evaporator of the type of refrigerator in which this invention is embodied consists of a coil within which the refrigerant is evaporated. Absorption of heat by the refrigerant as it evaporates causes the temperature of the coil to fall below the freezing point of water and results in the condensation of moisture from the air surrounding the coil and the freezing of the condensed moisture into an accumulation of frost and ice upon the evaporator coil. The accumulation of frost and ice acts as a thermal insulator which reduces the rate of absorption of heat by the refrigerant and thus cuts down the effectiveness of the evaporator as a cooling unit.

In the type of refrigerator in which this invention is embodied air is circulated over the evaporator by means of a fan or blower, the air itself thus being cooled. The cooled air then is circulated throughout the food storage cabinet where it absorbs heat and moisture. Thereafter the air is recirculated over the evaporator wherethe air again loses heat and moisture. a

In order to remove the insulating accumulation of frost and ice fromthe evaporator. it is necessary frequently to warm the evaporator and melt off the frost and ice. The evaporator can be warmed by merely stopping the refrigerating cycle, by admitting warm air to the evaporator, by heating the evaporator electrically, by passinghot refrigerant through the evaporator coil or by other means. In the preferred form of device described herein hot refrigerantis passed through the evaporator coil.

Initiation of defrosting maybe controlled by a timer which starts the defrosting at timed intervals (e.g. every four hours or every eight hours or at such other intervals as may be found best suited to the particular refrig- HQQ crating conditions under which the refrigerating apparatus is operated). Thermostatic controls and mechanisms which initiate defrosting after the refrigerator door has been opened a definite number of times also have been employed. Intervals of time, temperatures and numbers of door openings are very inexact criteria of the extent of frost and ice accumulation. Frost and ice accumulate more rapidly when relative humidity of ambient air is high; they accumulate more rapidly when doors are left open for long intervals; and many other variations in conditions affect the rapidity of accumulation.

It is an object of this invention to provide refrigerating apparatus in which initiation of defrosting occurs when frost and ice have accumulated on an evaporator to a sufficient extent.

It is another object of the invention to provide refrigcrating apparatus in which initiation of defrosting occurs when the passage of air over an evaporator is impeded to .a sufficient extent by accumulation of frost and ice on the evaporator.

Another object is the provision of refrigerating apparatus in which defrosting is initiated when frost and ice have accumulated on the evaporator to a sufficient extent and is terminated when defrosting has resulted in a sufficient rise of temperature.

Another object is the provision of refrigerating apparatus in which passage of hot refrigerant through an evaporator is initiated when frost and ice have accumulated on the evaporator to a suflicient extent.

And still another object is to provide refrigerating apparatus in which passage of hot refrigerant through an evaporator is initiated when the flow of air over the evaporator is impeded by sufficient accumulation of frost and ice.

Other objects and numerous advantages will be apparent upon perusal of the following description as illustrated by the accompanying drawings, in which:

Fig. I is a sectional elevational view of a refrigerator embodying the invention, some equipment being shown in elevation;

Fig. II is a diagram of refrigerating and defrosting apparatus that may be incorporated in the refrigerator of this invention; and

Fig. III is a sectional elevational view showing a modified form of air flow passageway over an evaporator.

This specification and the accompanying drawings describe and illustrate a preferred form of the invention but they are not intended to impose limitations on its scope.

In general, the refrigerator of this invention comprises a thermally insulated refrigerator cabinet 10 having a hinged thermally insulated front door 11. Attached to the ceiling of the refrigerator cabinet 10, j ust inside of the door 11, is an escutcheon 12 having an opening 13 which registers with an exhaust air port 14' through the top of the refrigerator cabinet 10.

Mounted on top of the refrigerator cabinet 10 is a removable case 15 which contains an evaporator 16 comprising a triple helical coil, or other plural layer coil, of tubing 17 having a continuous fin 18 preferably integral therewith. The said tubing is connected to a canister 19, known in this art as an accumulator, that may extend axially of the triple helical coil of tubing 17. The accumulator 19 adds volumetric capacity to the evaporator to avoid surging of liquid refrigerant through to the compressor. The triple coil of tubing 17 is supported within a housing 20 the mid portion of which is occupied by the triple coil with the exception of narrow spaces between the coil and the housing and between the adjacent turns of the coil itself. The housing 20 may be made of plastic material molded into shapes which fit together to adapt the housing to serve the multiple purposes of a container for the triple coil of tubing, a chamber through which air is circulated about the tubing, a blower and motor emplacement, a vane and switch emplacement and a thermostat emplacement.

The forward end of the housing 20 has one or more openings 21 which register with the exhaust air port 14 in the top of the refrigerator cabinet and are gasketed to form air tight joints therewith. The housing 20 also has a chilled air opening 22 adjacent its rear end, which opening registers with the upper end of a duct 23 through the top of the refrigerator cabinet 10 adjacent its rear Wall.

A blower motor 25 is mounted at the rear end of the housing 20 and rotates a radial discharge blower 26 which draws air from the interior of the refrigerator cabinet 10 through the opening 13 in the escutcheon 12, the port 14, the opening 21 and about the coil of tubing 17. The air flows axially into the blower and radially from the blower through the chilled air opening 22 of the evaporator housing 20 and the duct 23 into the interior of the refrigerator cabinet 10 where the air circulates throughout the interior. The space between the case and the evaporator housing is filled with thermal insulation to prevent any appreciable heat exchange between the contents of the evaporator housing and the ambient atmosphere.

Shown by the diagram of Fig. II are a motorized compressor 28 and a condenser 29. The motorized compressor 28 per se is a commercially available type and the condenser 29 consists of a coil of tubing shaped in a manner to function elfectively as a radiator of heat into the space into which it is installed. The compressor 28 is connected by means of a hot gas conduit 30 to one end of the coil of the condenser 29. The condenser 29 is connected by means of a restricted passage 31 to the end of the evaporator coil of tubing 17 remote from the connection between the coil of tubing 17 and the accumulator 19, the accumulator being connected in turn to a suction conduit 32 which leads to the compressor 28.

When the compressor is running it pumps refrigerant in the gaseous phasethrough the hot gas conduit 30 into the condenser 29, in which the refrigerant is cooled and condensed into the liquid phase, and from which it is subsequently emitted through the restricted passage 31 to the evaporator 16 where it absorbs heat from the air that is being drawn by the blower 26 through theevaporator housing 20 and around the tubing of the coil 17. Thereafter, the refrigerant is evacuated through the suction conduit 32 to be recompressed and reevaporated through successive cycles.

Leading from the hot gas conduit 30 to the evaporator coil of tubing 17 is a hot gas by-pass 33 which is normally closed by a valve 34 capable of being opened by a solenoid 35. The by-pass 33, the valve 34 and the solenoid 35 have functions in maintaining substantially unvarying temperatures within the refrigerator cabinet 10. These functions are not described in the instant specification since they do not enter into the instant invention.

In addition to the roles that the by-pass 33, the valve 34 and the solenoid 35 play in the maintenance of uniform temperatures within the refrigerator cabinet 10 they also function as important elements of the defrosting system of the instant invention. A defrosting system incorporating the by-pass 33, the valve 34 and the solenoid 35 may be set into operation manually and taken out of operation by a timer or other device after a predetermined interval, or aken out of operation by a thermostatic device when the temperature of a heat sensitive element has reached a predetermined interval. Other arrangements of timers, thermostats and so forth may be used to initiate or terminate defrosting.

In the preferred form of refrigerator embodying this invention air which is drawn by the blower 26 through the housing 20 and over the triple helical coil of tubing 17 circulates quite freely so long as the spaces between the coil and the interior of the housing and the spaces between the adjacent portions of the coil itself are not obstructed, but when those spaces are obstructed by accumulation of frost and ice, the flow of air is impeded and the impedance may reduce the speed and volume of air which passes into and emerges from the housing 20 to an extent that is an approximate reciprocal of the extent to which the frost and ice have accumulated.

Pivotally mounted at the vane emplacement 36 adjacent the path of air passing from the coil 17 to the blower 26, is a vane 37 which the force of gravity and/or the force of a spring holds in the air stream. While the flow of air is strong the vane is kept swung backwardly but when the flow of air is enfeebled by impedances of frost and ice that is accumulated on the evaporator coils the vane is swung forwardly by gravity, or by a spring, until the air stream impinges upon it nearly normally, i.e. perpendicularly. The vane 37 is fixed to a pintle 38 which extends into a switch box .39 where it is attached to a double throw switch 40.

While the air flow is strong enough to hold the vane 37 in the position in which it is shown in Fig. II, the circuit through the blower motor 25 is unbroken at the switch 40 and the blower 26 continues to operate. At the same time the circuit which activates the solenoid 35 is broken at the switch 40 so that the valve 34 remains closed. When, however, the evaporator 16 becomes clogged with frozen water condensation and the flow of air against the vane 37 becomes so weak that the vane can swing downwardly by gravity and open the circuit through the blower motor 25, the vane drops into the position in which it is shown in dash lines in Fig. II and causes the switch 40 to close the circuit which activates the solenoid 35, thereby opening the valve 34 and permitting hot gas to flow through the by-pass 33 into the evaporator coil, thus melting 013? the frost and ice. When the frost and ice are nearly melted the temperature of the heat sensitive element of a thermostat 41 located adjacent the evaporator coil 17 will open the circuit through the solenoid 35, thus closing the valve 34, and will simultaneously close a circuit through the blower motor 25 thus again drawing air over the evaporator coils.

The device of this invention limits the extent to which frost and ice can accumulate on the evaporator more exactly than it is possible for devices that are controlled by corollary conditions such as changes in temperature and humidity or by timing.

The device of this invention not only initiates defrosting just when defrosting is needed but it stops the circulation of air over the evaporator and throughout the refrigerator while the evaporator is being warmed. And it starts to =rechil1 the evaporator as soon as the temperature of the evaporator rises to a predetermined degree.

The above described system of hot gas defrosting air flow impedance for initiating defrosting and thermostatic means for terminating defrosting operates with the greatest economy and with the best protection against food spoilage.

The form of apparatus illustrated by Fig. III differs from that illustrated by Fig. I in that the vane 37a is located in the stream of air before the air passes over the evaporator tubing. The diagram of Fig. II applies to the form of Fig. 111 as well as to the form of Fig.1.

The appa atu he in ab ve d s ribed and illus rated in the accompanying drawings are exemplary only and the invention encompasses allmodifications falling within the spirit and scope of the teachings of this invention.

We claim:

-1. Refrigeration apparatus comprising, in combination; a thermally insulated cabinet; a case situated outside of said cabinet; said cabinet having an exhaust air port communicating with said case; an evaporator within said case; refrigeration system means causing said evaporator to chill air in said case; said case having a chilled air opening communicating with said cabinet; means for circulating air in a path through said exhaust port, across said evaporator, through said chilled air opening into said cabinet; an element yieldably displaceable by air disposed in said air path; heating means, controlled by the displacement of said element, being adapted to defrost said evaporator when a predetermined amount of frost or ice accumulated on said evaporator impedes the circulation of said air in said air path by a predetermined amount.

2. Refrigeration apparatus comprising, in combination; a thermally insulated cabinet; a case situated outside of said cabinet; said cabinet having an exhaust air port communicating with said case; an evaporator within said case; refrigeration system means causing said evaporator to chill air in said case; said case having a chilled air opening communicating with said cabinet; means for circulating air in a path through said exhaust port, across said evaporator, through said chilled air opening into said cabinet; an element yieldably displaceable by air disposed in said air path; defrost means, controlled by the displacement of said element being adapted to defrost said evaporator when a predetermined amount of frost or ice accumulated on said evaporator impedes the circulation of said air in said air path by a predetermined amount; said defrost means including a bypass valve connecting said evaporator with a hot gas conduit.

3. Refrigeration apparatus comprising, in combination; a thermally insulated cabinet; a case situated outside of said cabinet; said cabinet having an exhaust air port communicating with said case; an evaporator within said case; refrigeration system means causing said evaporator to chill air in said case; said case having a chilled air opening communicating with said cabinet; means for circulating air in a path through said exhaust port, across said evaporator, through said chilled air opening into said cabinet; an element yieldably displaceable by air disposed in said air path; defrost means, controlled by the displacement of said element being adapted to defrost said evaporator when a predetermined amount of frost or ice accumulated on said evaporator impedes the circulation of said air in said air path by a predetermined amount; means for deenergizing said air circulating means during said defrost operation.

4. Refrigeration apparatus comprising, in combination; a thermally insulated cabinet; a case situated outside of said cabinet; said cabinet having an exhaust air port communicating with said case; an evaporator within said case; refrigeration system means causing said evaporator to chill air in said case; said case having a chilled air opening communicating with said cabinet; means for circulating air in a path through said exhaust port, across said evaporator, through said chilled air opening into said cabinet; an element yieldably displaceable by air disposed in said air path; defrost means, controlled by the displacement of said element being adapted to defrost said evaporator when a predetermined amount of frost or ice accumulated on said evaporator impedes the circulation of said air in said air path by a predetermined amount; said defrost means including a bypass valve connecting said evaporator with a hot gas conduit; control means operative to stop said defrost operation.

5. Refrigeration apparatus comprising, in combination; a thermally insulated cabinet; a case situated outside of said cabinet; said cabinet having an exhaust air port communicating with said case; an evaporator within said case; refrigerationsystem means causing said evaporator to chill air in said case; said case having'a chilled air opening communicating with said cabinet; means for circulating air in a path through said exhaust port, across said evaporator, through said chilled air opening into said cabinet; an element yieldably displaceable by air disposed in said air path; defrost means, controlled by the displacement of said element being adapted to defrost said evaporator when a predetermined amount of frost or ice accumulated on said evaporator impedes the circulation of said air in said air path by a predetermined amount; said defrost means including a bypass valve connecting said evaporator with a hot gas conduit; means for deenergizing said air circulating means during said defrost operation; control means operative to stop said defrost operation.

6. Refrigeration apparatus comprising, in combination; a thermally insulated cabinet; a case situated outside of said cabinet; said cabinet having an exhaust air port communicating with said case; an evaporator within said case; refrigeration system means causing said evap' orator to chill air in said case; said case having a chilled air opening communicating with said cabinet; means for circulating air in a path through said exhaust port, across said evaporator, through said chilled air opening into said cabinet; an element yieldably displaceable by air disposed in said air path; defrost means, controlled by the displacement of said element being adapted to defrost said evaporator when a predetermined amount of frost or ice accumulated on said evaporator impedes the circulation of said air in said air path by a predetermined amount; said defrost means including a bypass valve connecting said evaporator with a hot gas conduit; means for deenergizing said air circulating means during said defrost operation; control means operative to stop said defrost operation and to energize said air circulating means including a heat sensitive member influenced. by the temperature of said evaporator.

7. Refrigeration apparatus comprising, in combination; a thermally insulated cabinet; a case situated outside of said cabinet; said cabinet having an exhaust air port communicating with said case; an evaporator within said case; refrigeration system means causing said evaporator to chill air in said case; said evaporator comprising a multi layer helical coil disposed in said case to effectively control air circulation through said case by the formation of frost and ice thereon; said case having a chilled air opening communicating with said cabinet; means for circulating air in a path through said exhaust port, across said evaporator, through said chilled air opening into said cabinet; an element yieldably displaceable by air disposed in said air path; defrost means, controlled by the displacement of said element being adapted to defrost said evaporator when a predetermined amount of frost or ice accumulated on said evaporator impedes the circulation of said air in said air path by a predetermined amount; said defrost means including a bypass valve connecting said evaporator with a hot gas conduit; means for deenergizing said air circulating means during said defrost operation; control means operative to stop said defrost operation and to energize said air circulating means including a heat sensitive member influenced by the temperature of said evaporator.

8. In refrigeration apparatus in combination; an evaporator coil comprising a multi-layer helical coil of tubing; an accumulator connected to said evaporator coil and positioned to extend axially within said multi-layer helical coil of tubing; means for enclosing said evaporator and accumulator assembly in a passageway; defrost means including a bypass valve connecting said evaporator with a hot gas conduit; means for directing a gaseous stream through said passageway to be cooled; and vane means positioned in said enclosing means in the path of said gaseous stream adapted to control said defrost means in response to the volume of flow of said gaseous stream through said passageway.

9. In refrigeration apparatus in combination; an evaporator coil comprising a multi-layer helical coil of tubing; and an accumulator connected to said evaporator coil and positioned to extend axially within said multilayer helical coil of tubing; heating means for defrosting said evaporator coil; said accumulator being disposed in heat exchange relationship with said evaporator coil such that the heating of said evaporator coil to defrost same isoperative to heat said accumulator positioned axially within said multi-layer helical coil causing vaporization of accumulated liquefied refrigerant in said accumulator.

References Cited in the file of this patent UNITED STATES PATENTS 

